Researchers realized a change needed to be made after administering the test to people suffering from primary-progressive aphasia, which strikes the young

We all suffer the occasional frustrating memory lapse, forgetting an actor’s name or a word we’re searching for. If these mental hiccups begin increasing in frequency, however, they could be a warning sign of impending dementia or other mental impairments.

As part of their evaluation for these problems, doctors use a facial recognition test. During this exercise, patients identify famous actors, politicians or sports players by name as images of the celebrities’ faces flash by.

But people may have been inadvertently failing some facial recognition tests, NPR reports. Famous faces of bygone years, including Emperor Hirohito and Jawaharlal Nehru, were stumping people for the wrong reasons.

The researchers realized a change needed to be made after administering the test to people suffering from primary-progressive aphasia, a type of cognitive impairment that impacts language abilities and often strikes a younger cohort (ages 40 to 65) than conventional dementia’s victims.

“We were giving the old test to 40-year-olds and 60-year-olds that came into the clinic,” tells Shots, “and many of them didn’t recognize the faces. We realized, talking to them, that it wasn’t because they couldn’t think of or say the name of . It was because they were too young to know the faces in these older tests.”

Now, in order to make sure the facial recognition test keeps up with the times, doctors are adding a few new characters to the list:

After the researchers subbed in some photos of more recent newsmakers, including Oprah Winfrey, Bill Gates, Princess Diana and Condoleezza Rice, the test worked reliably for the younger patients, too, Gefen says. (Not all the older photos were tossed, of course — Albert Einstein, Lucille Ball, and Winston Churchill, for example, continued to be familiar to most of the younger test-takers.) And by adding a feature that allowed the respondents to talk a bit about the celeb, even if they couldn’t come up with the name, the researchers could tease out subgroups of the disorder.